Many implantable medical devices have a coating in which the coating can perform various functions, such as improving the biocompatibility of the device or serving as a drug delivery system. Also, certain types of porous coatings have been proposed to encourage the migration and normal growth of tissue onto the coating. This feature is beneficial in medical devices because it can enhance its effectiveness and reduce the incidence of unwanted effects and complications such as thrombosis, infection, scarring, or abnormal tissue growth.
One type of porous coating is a porous carbon coating, which has been demonstrated to be highly biocompatible. Porous carbon coatings are able to serve as localized drug delivery systems, which is beneficial in improving the effectiveness of medical devices. Therapeutic agents can be loaded into a porous carbon coating on a medical device and released into the surrounding fluid or tissue after implantation.
There are various methods for creating a porous carbon coating on a medical device, including chemical vapor deposition, physical vapor deposition, and sputtering. Porous carbon can also be created by carbonization in which a carbon-containing precursor material, such as wood, cellulose, coal, or synthetic polymer is pyrolysed. During pyrolysis, the carbon-containing precursor material decomposes, with most of the non-carbon elements, such as hydrogen, nitrogen, and oxygen being removed in tarry or gaseous form. The resulting carbonization of the carbon-containing precursor material transforms it into a solid porous carbon mass.
U.S. Patent Publication No. 2005/0079200 (Rathenow et al.), whose entire disclosure is incorporated by reference herein, describes porous carbon coatings on medical devices created by coating the medical device with a polymer film and then pyrolysing the polymer film by oven heating at high temperatures. The oven heating method of Rathenow results in the uniform carbonization of all parts of the medical device coated with the polymer film.